Aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid are used to produce a variety of polyester products, important examples of which are poly(ethylene terephthalate) and its copolymers. These aromatic dicarboxylic acids are synthesized by the catalytic oxidation of the corresponding dialkyl aromatic compounds which are obtained from fossil fuels (US 2006/0205977 A1). There is a growing interest in the use of renewable resources as feed stocks for the chemical industries mainly due to the progressive reduction of fossil reserves and their related environmental impacts.
FDCA is a versatile intermediate considered as a promising closest biobased alternative to terephthalic acid and isophthalic acid. Like aromatic diacids, FDCA can be condensed with diols such as ethylene glycol to make polyester resins similar to polyethylene terephthalate (PET) (Gandini, A.; Silvestre, A. J; Neto, C. P.; Sousa, A. F.; Gomes, M. J. Poly. Sci. A 2009, 47, 295). FDCA has been prepared by oxidation of 5-(hydroxymethyl) furfural (5-HMF) under air using homogenous catalysts (US2003/0055271 A1 and Partenheimer, W.; Grushin, V. V. Adv. Synth. Catal. 2001, 343, 102-111) but only a maximum of 44.8% yield using Co/Mn/Br catalysts system and a maximum of 60.9% yield was reported using Co/Mn/Br/Zr catalysts combination. Recently we report a process for producing furan-2,5-dicarboxylic acid (FDCA) in high yields by liquid phase oxidation of 5-HMF using Co/Mn/Br catalysts system that minimizes solvent and starting material loss through carbon burn. Heterogeneous catalysis oxidation of 5-HMF using ZrO2 mixed with platinum (II) acetylacetonate in water has also been reported (U.S. Pat. No. 7,700,788 B2) but due to very low solubility of FDCA in water, this process needs to be conducted under very dilute conditions to avoid precipitation of FDCA on the catalysts surface which makes the process not economical. Another heterogeneous catalysis oxidation of 5-HMF is reported (U.S. Pat. No. 4,977,283) using molecular O2 and a Pt/C catalyst. High FDCA yield was achieved but at the extra expense of feeding purified O2 and continually adjusting pH via sodium hydroxide addition. The reaction product was the disodium salt of FDCA leading to a wasteful salt by-product in the conversion to FDCA. A high yield process (minimum of 90% FDCA yield), to produce a dry purified FDCA product is disclosed in this invention report.